The long-term goal of this proposed research is to further elucidate the mechanisms underlying primary ciliary dyskinesia (PCD). As many as 1:15000 individuals are estimated to have PCD, which typically manifests as chronic respiratory tract infection, male infertility, often some degree of situs reversal due to lost or impaired cilia motility, and in rare cases, cystic kidney disease. To date, multiple dyneins have been associated with PCD, however, several other linked genetic loci have also been implicated in the disease. The genes relevant to development of PCD in these genetic intervals have yet to be identified. Multiple zebrafish mutants harboring lesions within genes that affect ciliary structure and function are currently being studied by this and other laboratories. While a large number of the zebrafish mutants exhibit defects in cilia length and subsequently, their ability to beat properly, only a few possess cilia of normal length that fail to beat. One such mutant is schmalhans, and we will use it to identify genes important for cilia motility. We hypothesize that the zebrafish paralyzed cilia mutant schmalhans harbors a mutation in a novel gene required outer dynein arm assembly. These embryos are characterized by a curved body axis, immotile cilia in the nose, kidneys, spinal canal, and develop kidney cysts within 3 days post-fertilization. By identifying the genetic lesion in schmalhans, we also hope to uncover and study the function of a new gene involved in proper kidney function. Our hypothesis will be tested by the following specific aims: Aim1.To identify the schmalhans gene through positional cloning and in silico assembly of the genetic interval, morpholino loss of function studies, and rescue using synthetic RNA. Aim 2. To characterize the schmalhans gene through expression analysis, comparison to mammalian homologs, and collaboration with PCD investigators. Aim 3. To identify the pathway(s) through which schmalhans acts to affect cilia motility by identifying interacting proteins and the domains of Schmalhans required for those interactions. Ultimately, it is our hope that this research will aid others to better identify and treat PCD patients by equipping them with a more complete understanding of the underlying disease mechanism. In addition, treatment of other health problems linked to cilia dysfunction, such as polycystic kidney disease, may be assisted by these studies.